Power transmission

ABSTRACT

A directional valve for a hydraulic power system has a body adapted to be clamped into a bank of valves and has a spool slidable within the body to direct fluid flow between a pressure fluid source and a hydraulic motor. The body includes auxiliary valves such as a load compensating flow regulator, a load-drop check valve, a cylinder port relief valve, and a cylinder port anti-cavitation valve and the spool includes one or more counterbalance valves. Load sensing passages in the body direct load pressure to the compensator valve and to the pressure source for controlling the volume of fluid delivered from the source. The body is designed for maximum symmetry with the spool bore near the middle of the iron mass to minimize distortions caused by aging of the iron by temperature differences and by the pressure force of the fluid.

United States Patent 1 Farrell et a1. Nov. 27, 1973 POWER TRANSMISSIONPrimary ExaminerSamue1 Scott 1 Assistant Examiner-Ara S. Lazarus [75]Inventors: Robert G. Farrell, Royal Oak;

Carl R. y Warren, both of Att0rneyThe0dore Van Meter Michv [57] ABSTRACT[75] Asslgnee F" Rand Corporation Troy A directional valve for ahydraulic power system has a body adapted to be clamped into a bank ofvalves and [22] Filed: Apr. 18 1972 has a spool slidable within the bodyto direct fluid flow between a pressure fluid source and a hydraulic mo-1 PP 245,103 tor. The body includes auxiliary valves such as a load US.Cl 137/614.2, 137/608, 137/625.68

compensating flow regulator, a load-drop check valve, a cylinder portrelief valve, and a cylinder port anticavitation valve andthe spoolincludes one or more counterbalance valves. Load sensing passages in thebody direct load pressure to the compensator valve and to the pressuresource for controlling the volume of fluid delivered from the source.-The body is designed for maximum symmetry with the spool bore nearthemiddle of the iron mass to minimize distortions caused by aging of theiron by temperature differences and by the pressure force of the fluid,

7 Claims, 7 Drawing ELgures [51] Int. Cl. F16k 13/00, F16d 1/00 [58]Field of Search 137/6142, 614.01, 137/614, 608, 625.68

[56] References Cited UNITED STATES PATENTS 3,357,451 12/1967 Tennis137/6142 X 3,375,845 4/1968 Behm 137/614 X 3,255,777 6/1966 Rice eta1.... 137/625.68

3,014,498 12/1961 Stephens..... 137/6142 X 3,556,147 1/1971 Sizer137/608 PAIENIEUnnvzv 1975 POWER TRANSMISSION Directional valves for usein hydraulic systems commonly utilize a spool slidable in a bore in thevalve body to direct fluid flow between the source and the fluid motoror other service device. Particularly in circuits supplying more thanone service device, various auxillary valves are required to minimizethe interaction of one circuit upon another when two or more are inoperation. The introduction of such auxiliary valves into the same bodywith the spool type valve or as attachments thereto has heretoforerequired bulky and heavy construction and has, so far as bank typevalves are concerned, complicated the problem of clamping and sealingtogether the various sections of the bank, requiring additional clampingbolts and extra space in the body to receive them in isolation from theauxiliary valves and their associated passages.

Spool type directional valves designed for high operating pressures ofthe order of 4,000 and 5,000 psi. require very close fits between thespool and the body if leakage losses are to be kept within acceptablelimits. Close fits, however, become sensitive to body distortions whicharise from the natural growth of iron castings, from the unequalexpansion of the body due to temperature rises, and from high pressurewithin the internal passages in the body. These distortions make thespool difficult to shift manually and frequently cause completeseizures.

Another difficulty which has arisen with multiple unit or bankablevalves arises when two or more circuits are simultaneously in operationand it is desired to throttle or meter the flow to each of them. If theloads require different operating pressures and fluctuate from moment tomoment, reliable speed control of the lesser loaded service device ordevices becomes very difficult.

The present invention aims to provide a spool type hydraulic valve whichmay be incorporated in a bank of valves and which may utilize any or allof the various auxiiary valves which particular applications require,which may operate with close fits for very high pressures and with thesubstantial absence of body distortions and in which good metering orspeed control is achieved under all conditions.

These advantages are achieved by the provision of a hydraulic valve unitcomprising a generally rectangular body having a spool bore extendingfrom end to end of the rectangle and lying substantially mid-way betweenits sides, the body having a thickness approximately double the spoolbore diameter, a supply port traversing the body thickness and lyingmid-way between the ends of the body, a pair of holes to receiveclamping bolts traversing the body thickness and spaced from the supplyport toward the ends of the body, a pair of exhaust ports traversing thebody thickness and spaced from said holes toward the ends of the body,the supply port, the bolt-receiving holes and the exhaust ports lyinggenerally along a line parallel to and at one side of the spool bore,passages connecting the supply port and the exhaust ports with the spoolbore, passages on the other side of the bore extending to that side ofthe body to constitute service ports, and a flow directing spoolslidable in the spool bore, the body having substantially equalquantities of metal on either side of the spool bore whereby distortionof the bore due to unequal expansion of the metal caused by aging or bytemperature rise is minimized.

IN THE DRAWINGS FIG. 1 is a top view of a valve bank incorporating apreferred form of the present invention.

FIG. 2 is a cross section on line 2-2 of FIG. 1.

FIG. 3 is a cross section on line 3-3 of FIG. 1.

FIG. 4 is an end view of the valve bank of FIG. 1.

FIG. 5 is a view corresponding to a fragment of FIG. 3 and illustratinga modification.

FIG. 6 is a circuit diagram of a hydraulic power transmission systemcorresponding to FIGS. 1 through 4.

FIG. 7 is a circuit diagram of a hydraulic power system incorporatingthe modification of FIG. 5.

The valve bank illustrated in FIG. 1 comprises a supply and returnsection 10, two sectional valves 12, and an end plate 14, all of whichare clamped together by two through-bolts 16. As seen in FIG. 4, thevarious sections of the bank have flat mating surfaces 18 which aregasketed to seal the fluid passages extending between the units of thebank. These surfaces and gaskets extend only over about the lower thirdof each of the sections 10 and 12.

Referring now to FIG. 2, each valve section 12 comprises a body 20 whichis generally of rectangular form with left and right-hand ends and topand bottom sides. Substantially mid-way between the sides is a valvespool bore 22 extending from end to end and receiving a slidable spool24. Thus, the bore 22 has substantially equal amounts of metal, usuallycast iron, on either side of the spool. The body thickness is preferablyabout twice the spool diameter or a little greater.

The body 20 at the lower side in FIG. 2 contains a symmetrical array ofpassages and holes extending through the thickness of the body. Theseinclude the supply port 26, the two unnumbered holes for the bolts 16and the two exhaust ports 28. Internal passages 30 connect the exhaustpassages 28 with the bore 22 and extend upwardly approximately an equaldistance into the other side of the body. A load compensating valve 32is biased by a spring 34 and the hydraulic force difference between itstop and bottom areas to a variably restrict flow from supply port 26 tothe bore 22 at its center portion. A ballcheck valve 36 within the valve32 acts to prevent dropping of a load in the event another valve in thebank should not be maintaining adequate pressure in the connectingsupply port 26. The lower side of the body contains a pair of sensingpassages 38 which communicate with the bottom of the load compensatingvalve 32 and also, at the right-hand end, connect through a check valve40 with a throughport 42 extending from section to section of the bank.

On the upper side of the spool bore 22, there is provided a pair ofservice passages 44 and 46 extending to the usual terminals forconnection with a fluid motor or other service device. The upper sideextensions of the exhaust passages 30 provide communication forauxiliary valves such as a service port relief valve 48 and a serviceport anti-cavitation valve 50. Alternatively more complex auxiliaryvalves, not illustrated, may combine these functions for each serviceport and can be placed at these locations. Cross port relief valves canbe incorporated.

The valve spool 24 is preferably hollow and contains one or morecounterbalance valves 52 which control communication between a firstseries of escape holes 54 and a second series 56. The counterbalancevalves are spring biased toward the center and one or the other isopened by supply pressure in the central passage 58 whenever the valveis shifted to the right or to the left. The spool 24 also has lands 60which selectively open one or the other of the sensing passages 38 whenthe valve is shifted. Because the spool is nonrotatable in its bore, theholes 54 or 56 do not uncover sensing passages 38 when the valve isshifted, so that only one sensing passage 38 at a time can be opened,and that is the one then communicating with a service passage 44 or 46.

Referring now to FIG. 3, the supply and return section comprises asupply passage 62 which connects with the supply port 26 and a returnpassage 64 which connects with both exhaust passages 28. A central bore66 contains an unloading valve 68 which controls communication betweenpassages 62 and 64 and is spring biased downwardly. The sensing passage42 which extends through the bank of valves communicates by a passage 70contained within a boss 72 (FIGS. 1 and 4) with the upper end of thebore 66. A restricted passage 72 through the upper head of the valve 68allows a continuous restricted flow out of the sensing passages 38, 42,and 70. The passage 42 has a terminal connection 74 which is plugged foruse with supply sources consisting of a fixed displacement pump and anunloading valve, commonly referred to as an open center system,

, and which may be connected to the control device of a variabledisplacement pump when used for a closed center system with the modifiedvalve illustrated in FIG. 5.

In FIG. 5, the supply and return section 10 has in place of theunloading valve 68 and the sensing passage 70, only a balanced reliefvalve 75, its upper piston head being of slightly smaller diameter thanits lower piston head, and which serves to limit the maximum pressure inthe supply passage 62.

FIG. 6 illustrates diagrammatically a hydraulic system of the opencenter type in which a fixed displacement pump 76 withdraws fluid from areservoir 78 and delivers it to the supply passage 62 of the section 10and to the supply ports 28 of each of the sections 12. Exhaust ports 28of sections 12 and return passage 64 of section 10 return fluid to thereservoir 78. The service passages 44 and 46 connect with servicedevices such as a rotary fluid motor 80 and the hydraulic cylinder 82.

In the central position of the valve spool 24, as illustrated in FIG. 2,the sensing passages 38 are closed by the spool land 60 and consequentlypressure therein is dissipated through the restricted orifice 72 (FIG.3) so that the entire delivery of the pump 76 is bypassed from passage62 to passage 64 by the consequent opening of the valve 68. When valvespool 24 is shifted, for example to the right in FIG. 2, fluid issupplied from port 26 through the load compensating valve 32 and theload drop check valve 36 to the service passage 44 and the servicedevice. Fluid returning from the service device enters passage 46 whereit meets the holes 54 of the spool which at the start are closed offfrom the holes 56 by the counterbalance valve 52. However, as operatingpressure builds up in passage 44, this shifts the counterbalance valveto allow communication from holes 54 to holes 56 and exhaust passage 30.The counterbalance valve 52 prevents overrunning of the service deviceat a speed faster than'the pump can deliver fluid to it. In the eventthat the service device is subject to extreme overloads, the serviceport relief valve 48 will open to limit the pressure in the servicepassage 44 and the anticavitation valve 50 will open to maintain theservice passage 46 filled.

With the valve spool 24 shifted to the right, the land 60 at theright-hand end uncovers the right-hand sensing passage 38. This causesthe load compensating valve 32 to maintain a constant pressure dropacross the spool-body orifice controlling flow of supply fluid into theservice passage 44. In this way, the quantity of fluid passing to theservice passage 44 is maintained constant at a given position of spool24 regardless of the difference in pressure between supply port 26 andservice passage 44.

In addition, the rate of fluid supply from the inlet passage 62 to thesupply port 26 in section 10 is automatically adjusted to meet the totalrequirements of the valve bank. This takes place through the action ofthe unloading valve 68 which responds to the differential pressurebetween that in passage 62 and that in the sensing passage 42-70. Thislatter receives the highest of the various pressures in sensing passages38 of the diflerent valve sections. Sections having lower pressures attheir service devices are cut off from the through-sensing passage 42 byclosure of their respective check valves 40.

Referring now to FIG. 7, the hydraulic circuit diagram there illustratedis similar to FIG. 6 except that the pressure source is a variabledisplacement pump 84 and that the system is a closed center system.Rather than the unloading valve 68 and its controlling passage 70 inFIG. 3, the section 10 contains the relief valve 76 of FIG. 5. Inaddition, the through-sensing passage 42 is connected by means of theterminal 74 with a pilot valve 86 which controls the displacementregulator 88 of the pump 84. The pilot valve 86 is subject to deliverypressure through a conduit 90 at its right end and, at its left-handend, to the highest of the pressures in the service ports 44 astransmitted through the sensing passages 38, 42, 74, and 92. The pilotvalve 86 may contain an internal restricted passage 94 corresponding tothe passage 72 illustrated in FIG. 3. By this means, the delivery rateof the pump 84 is maintained at that necessary to supply only the totalrequirements at any moment of all the valve units or sections in thebank which, of course, depends upon the manual position of adjustment ofeach valve spool.

The design of the valve body 20 (FIG. 2) places substantially equalamounts of iron on either side of the spool bore 22 so that aging andtemperature expansions of the body take place uniformly on both sides ofthe bore 22 and do not introduce distortions causing the bore to departfrom a true right cylinder. In addition, the location of the joining orsealing surfaces 18 between adjacent units of the valve bank issymmetrical with respect to the clamping bolts 16 with the supply port26 at the center and the exhaust ports 28 at either end, also thissurface and the three bolts are located below the valve spool bore. Anydistortion due to these bolts will not cause bind. This symmetricalconstruction avoids sealing difficulties previously experienced withother designs.

We claim 1. A hydraulic valve unit comprising a generally rectangularbody having a spool bore extending from end to end of the rectangle andlying substantially mid-way between its sides, the body having athickness approximately double the spool bore diameter, a supply porttraversing the body thickness and lying mid-way between the ends of thebody, a pair of holes to receive clamping bolts traversing the bodythickness and spaced from the supply port toward the ends of the body, apair of exhaust ports traversing the body thickness and spaced from saidholes toward the ends of the body, the supply port, the bolt receivingholes, and the exhaust ports lying generally along a line parallel toand at one side of the spool bore, passages connecting the supply portand the exhaust ports with the spool bore, passages on the other side ofthe bore extending to that side of the body to constitute service ports,and a flow directing spool slidable in the spool bore, the body havingsubstantially equal quantities of metal on either side of the spool borewhereby distortion of the bore due to unequal expansion of the metalcaused by aging or by temperature rise is minimized.

2. A valve unit as defined in claim 1 having a pair of sensing passagesextending from the spool bore toward the one side of the body, apressure compensator valve in the supply passage and having an endexposed to the sensing passages.

3. A valve unit as defined in claim 2 wherein means is provided forcommunication of only one sensing passage with only one of the servicepassages at any one time.

4. A valve unit as defined in claim 1 having a relief valve connectingone of the service ports with an exhaust passage at the other side ofthe spool bore.

5. A valve unit as defined in claim 1 having a check valve connectingone of the exhaust passages with the service passage at the other sideof the spool bore.

6. A valvespool as defined in claim 1, the spoolbeing hollow andcontaining at least one counterbalance valve responsive to supplypressure in one service port to open the other service port to exhaustthrough the hollow spool.

7. A valve unit as defined in claim 1, the spool being hollow andcontaining a pair of counterbalance valves, means on the spool forconnecting one counterbalance valve to the supply passage when the spoolis shifted and for disconnecting the other counterbalance valve at thesame time.

I a i

1. A hydraulic valve unit comprising a generally rectangular body havinga spool bore extending from end to end of the rectangle and lyingsubstantially mid-way between its sides, the body having a thicknessapproximately double the spool bore diameter, a supply port traversingthe body thickness and lying mid-way between the ends of the body, apair of holes to receive clamping bolts traversing the body thicknessand spaced from the supply port toward the ends of the body, a pair ofexhaust ports traversing the body thickness and spaced from said holestoward the ends of the body, the supply port, the bolt receiving holes,and the exhaust ports lying generally along a line parallel to and atone side of the spool bore, passages connecting the supply port and theexhaust ports with the spool bore, passages on the other side of thebore extending to that side of the body to constitute service ports, anda flow directing spool slidable in the spool bore, the body havingsubStantially equal quantities of metal on either side of the spool borewhereby distortion of the bore due to unequal expansion of the metalcaused by aging or by temperature rise is minimized.
 2. A valve unit asdefined in claim 1 having a pair of sensing passages extending from thespool bore toward the one side of the body, a pressure compensator valvein the supply passage and having an end exposed to the sensing passages.3. A valve unit as defined in claim 2 wherein means is provided forcommunication of only one sensing passage with only one of the servicepassages at any one time.
 4. A valve unit as defined in claim 1 having arelief valve connecting one of the service ports with an exhaust passageat the other side of the spool bore.
 5. A valve unit as defined in claim1 having a check valve connecting one of the exhaust passages with theservice passage at the other side of the spool bore.
 6. A valve spool asdefined in claim 1, the spool being hollow and containing at least onecounterbalance valve responsive to supply pressure in one service portto open the other service port to exhaust through the hollow spool.
 7. Avalve unit as defined in claim 1, the spool being hollow and containinga pair of counterbalance valves, means on the spool for connecting onecounterbalance valve to the supply passage when the spool is shifted andfor disconnecting the other counterbalance valve at the same time.
 8. Ahydraulic power system including a source of pressure fluid having anelement controllable to deliver fluid at a rate determined by thepressure lever in a controlling conduit, and a directional valve forsupplying pressure fluid to a load device, the valve comprising a bodyand a spool slidable therein to direct fluid in one direction or theother to the load device, means in the body for sensing the pressurelevel at the load device and connected by the controlling conduit to thecontrollable element of the source, and a flow regulating valveassociated with the directional valve and also connected with thesensing means.
 9. A power system as defined in claim 8 including asecond directional valve having a flow regulating valve connected withthe sensing means, and valves in the sensing means for isolating thepressure level at the load device which is lower from that which ishigher.
 10. A power system as defined in claim 8 wherein the sensingmeans includes an individual check valve in each directional valve forisolating the pressure level at the load device which is lower from thatwhich is higher.